There’s not much “war surplus” around these days, so old-time stores like Burden’s have concentrated on hydraulic and pneumatic components, electronic parts, industrial leftovers, and discounted tools. As with all surplus outlets, you are at an advantage if you have some experience with this sort of merchandise; there are few explanations beyond the specifications.
Imaginative use of a catalog like this can lead to unexpected new capabilities; indiscriminate use can lead to an overstuffed garage.